This invention is directed to a fill tube and plunger rod and to assemblies of these fill tubes and plunger rods that are mounted on pouch packaging machines. The plunger rods are located within hollow interiors of the fill tubes and include a bulbous valve thereon that allows for the control of the velocity of discharge of products from the fill tubes.
Because of technical advances in pouch forming and filling machines, more and more food products can be dispensed in product pouches as opposed to dispensing in more conventional cans and bottles. Certain products, however, are very difficult to package in pouches. These includes very thin liquids whose viscosity borders on that of water and solid component containing soups and sauces.
The fill tubes on many prior pouch packaging machines are nothing more than hollow tubes having an open end. A feed pump mechanism controls the flow and the amount of product introduced into the fill tube. A metered amount of product is injected in one end of the tube and this displaces a like amount of product from the other end. While this type of tube is useful for certain products having medium viscosity, as for instance catsup and salad dressing, it is totally unsuitable for very thin "runny" type products. For a very thin liquid, as for instance a liquid of a viscosity of about 40 to 50 centipoise, if a very narrow, small diameter fill tube is utilized the product remains in the tube because of surface tension and thus can be controlled via a cycling metering pump. However, because the tube is very narrow, fill rates are very slow. If, to increase the fill rate, a larger diameter tube is utilized, sometimes the surface tension between the liquid product and the fill tube is not sufficient to retain the contents of the fill tube between cycles of the metering pump. In two adjacent pouches one pouch may receive the correct amount of product but its adjacent pouch is over filled because, not only is the metered aliquot of product discharged as the pump cycles, but the total contents of the fill tube are also discharged into the pouch because of loss of surface tension between the product and the fill tube.
Quite contrary to a thin, runny product, it has also been very difficult to package products having particulate matter therein, as for instance soups and sauces, like oriental sauces. Because these products have large pieces of solid product in them, large tubes must be used. This prevents the use of an open end fill tube. Prior attempts to incorporate a valving mechanism on the end of a large fill tube have been less than satisfactory. Such prior attempts to utilized valving mechanisms generally resulted in inappropriate comminution of the solid part of the product by the valving mechanism. A consumer would find a pouch of water chestnuts very unappetizing if, in fact, all the water chestnuts have been shredded by the valving mechanism utilized to control the filling of a pouch with this product.